Method for producing novel stabilizers for aqueous formaldehyde solutions and product

ABSTRACT

NOVEL STABILIZERS FOR CONCENTRATED AQUEOUS FORMALDEHYDE SOLUTIONS ARE PRODUCED BY REACTING AN ORGANIC HALOGENATED SILANE AND A LONG CHAIN CARBOHYDRATE IN PYRIDINE. THESE STABILIZERS ARE EFFECTIVE OVER THE TEMPERATURE RANGE FROM ABOUT 20*C. TO ABOUT 90*C. THE STABILIZERS OF THIS INVENTION DO NOT EXHIBIT ANY APPRECIABLE FOAMING AND PREVENT POLYMER FORMATION AT ROOM TEMPERATURE.

United States Patent METHOD FOR PRODUCING NOVEL STABILIZERS FOR AQUEOUSFORMALDEHYDE SOLUTIONS AND PRODUCT 3,637,861 Patented Jan. 25, 1972because they will lead to undesirable properties when the formaldehydeis used in certain reactions.

Other various compounds have been proposed but again, the amount neededis usually prohibitively large Frederic Shelton, Tacoma, Wash assignorto 5 so as to effect the end product or to be too expensive. ReichholdChemicals, Inc White Plains, NY. Only a few stabilizers have been foundto be effective N D i Fil d 11, 1970, S 13,70 at very lowconcentrations, i.e. 101000 p.p.m., for an I t. Cl, C07 47/04 extendedperiod of time. These include high organic poly- U.S. Cl. 260-606 Claimsmer colloids (U.S. Pat. No. 3,137,736) and noncolloidal 10 alkylacrylate homopolymers (U.S. Pat. No. 3,359,326). Certain carbohydratese.g. hydroxypropyl cellulose or ABSTRACT OF THE DISC OS Emethylcellulose all have a stabilizing effect. However, Novelstabilizers for concentrated aqueous formaldethelr Performance leaveSmuch to he desired in that y hyde solutions are produced by reacting anorganic halotend to cause considerable foaming. Although thisfoamgenated silane and a long chain carbohydrate in pyridine. mg can heoohtrolled gh the addition of a defoamer These stabilizers are effectiveover the temperature range Such as a Slllcorle tylle defoarher, the q yof the f o about C to about 90 C- The stabilizers f defoamer required isextremely critical and tends to form this invention do not exhibit anyappreciable foaming hohhorhogeholls dlsperslolls- Alrerhatltely thequantities d prevent polymer f ti at room temperature required are solarge as to interfere with many processes 20 for which the formaldehydeis used. Although there are a great number of organic silicone compoundsavailable, This invention relates to formaldehyde and in particular nonePossess the ablllly to Stabilize f rm ldehyde 0111- to the stabilizationof aqueous solutions of formaldehyde trons in concentrations rangingfrom about 30 to about 80%. It 15, therefore, all obleet of thlslrlyerltloh to Prodllee Concentrated aqueous Solutions of formaldehydeare concentrated aqueous formaldehyde solutions which are ferred overdiluted solutions because diluted solutions are Stable at m temperature.cumbersome to handle and costly to transport. However, a further ohleorof thls lhvehtloh to Produce novel as has long been known, aqueoussolutions of f m stabilizers for concentrated aqueous formaldehydesoluhyde in concentrations greater than about tend to tions which areeffective in very low concentrations and become cloudy and precipitateformaldehyde polymers 30 for erftehrled Perlollls of h unless stabilizedor stored between 50-100 0. Even if It 18 Bull another oblect of thlsInvention to produce stored at these elevated temperatures, theunstabilized Stable aqueous formaldehyde solutions containing 110concentrated formaldehyde solutions Will show polymer methanol;formation within a matter of hours. Therefore, stabilizers And It 15 yetanother object of this lhverltlorl to Produce h e been ro o ed anddeveloped to prevent the formg; stable aqueous formaldehyde SOlUtlOIlSWith 10W methtion and/or separation of the formaldehyde polymers at 8 01Content. 0 I lower storage temperatures. In the past, compounds used AndStlll another ohleel of thlS ln tlon 1s to produce for stabilizingconcentrated aqueous formaldehyde soluq o formalrlehyde solutlohs, Whlohdo not lhdlloe y tions have had the disadvantage of either beingrequired 40 material amount of foaming. in such a high concentration asto make them unpractical These and other hl thlS mventlon W111 become orbeing susceptible to a high degree of foaming. The pparent to thoseskilled in the art as th1s description stabilizers of this inventionhave neither of these draw- P s- I I backs as they are eifective inconcentrations as low as has now e found that the above ohleots can be10 p p.m, and cause a minimum of foaming. achieved by adding smallamounts (from about 10 p.p.m.

Methyl alcohol has been widely used as a stabilizer for to about 1000P-P- of the ct on product of an orpreventing polymer formation. It ispresent in concentragahlo halogenated Srlahe and carbohydrate P y totions ranging from 8 to about 15% in standard commer- Concentrated q oformaldehyde solllhorla cial 37% aqueous formaldehyde solutions.However, these Table I clearly illustrates the unexpected improvementsrelatively large quantities are quite unacceptable at times, embodied bythis invention.

TABLE I [Comparison of stability and antifoam abilities] Foam test (mm.of foam) Stability Dll'gtizg I 2 days at 50 C. 2 days at 40 C. shaking 4min. 10 min. 3 days it? hlifiiyifliifihii ii .filfti i'::::::::::::::::flilliabli'aataasaj::jj Siff'it 9%. 33%;: N03! N032 Norl Nori c) Mixtureof hydroxypropylmethyl cellulose and Clear 01 1 13 3 3 mm. ppt. on 25 2515 8 n figiiilli ggfifi ii ih i cellulose trimethylchloro- Clear Legscggi l lgy 1 mm. ppt: None None None a l b iglik control (no stabilizer)5 mm. ppt. on bottom... Cloudy, 10 mm. ppt None None None 1 Preparedasper Example VI.

. .-A throu h D were re ared by taking grams of 53% formaldehyde andtreating it with 0.01 gram of the subject material. t tfl ilft g l a rscontaini g treated i rn i aldehyde were stored on our oven at constanttemperature and observed. a h Foam test.-Standard test tubes containingequivalent amounts of solution were shaken for 15 seconds and thenstored in an oven at 50 C. and t e rate of foam dispersion was observed.

Solution A, which includes only hydroxypropylmethyl for a short periodand then the product is poured onto an cellulose as a stabilizer hasfairly good stability properevaporating dish where the pyridine isevaporated off. The ties namely one mm. precipitate and cloudy after twodays resulting material, when mixed with water, is then ready storage at50 C. but foams considerably (27 mm.) and for use as a formaldehydestabilizer. still retains a 10 mm. head of foam after three days. Solu-The concentrated aqueous formaldehyde solutions to be tion B istrimethylchlorosilane alone and produces no stabilized may be preparedby any of the methods well foam during the foam test but is noteffective as a staknown to the art. bilizer, allowing 5 mm. ofprecipitate after two days of The following detailed descriptions andexamples are storage at 50 C. and 8 mm. of precipitate and a cloudypresented to further illustrate this invention and are not Solutionafter two days of storage at 40 C. 10 intended to limit it to theparticular details set forth Test solution C is a mol for mol mixture ofhydroxythfieinpropylmethyl cellulose and trimethylchlorosilane. ThisEXAMPLE I solution gave fairly good stabilization; no precipitationafter two days storage at 50 C. but was cloudy and had 3 mm. precipitateafter two days storage at 40 C. However, this solution gave largeamounts of foam, 25 mm., which persisted and still retained 8 mm. offoam after standing for three days.

When test solution D was prepared, which is the reaction product ofhydroxypropylmethyl cellulose and trimethylchlorosilane, totallyunexpected results were obtained. Stability was greatly improved, nowhaving no precipitate after two days storage at 50 C. and only one mm.of precipitate after being stored for two days at 40 C. with nocloudiness. Foaming was almost entirely eliminated having only fifteenmm. of foam directly after shak- Two grams of hydroxypropylmethylcellulose is mixed into ml. of anhydrous pyridine. One gram oftrimethylchlorosilane is then added dropwise with stirring into thehydroxylpropylmethyl cellulose-pyridine mixture. After stirring forabout five minutes the reaction is completed the pyridine is evaporatedoff. The resulting white product is dissolved in enough distilled waterto make a 2% solution. This solution is then suitable for use as aformaldehyde stabilizer.

A freshly prepared aqueous solution of 52% formaldehyde was divided into100 gm. samples. To different samples were added different amounts ofthe aqueous solution from above. To the control sample nothing was andthe jelly-like solution is poured out on a dish where,

ing which disappeared Completely in less than four added. All of thesamples were allowed to stand for four utes- The Stability as mp tohydroxypropylmethyl weeks at C. The samples were periodically checkedfor cellulose alone or in a mixture increased considerably and lo dine ad precipitate formation. The results obtained the foaming was almostcompletely eliminated as com- 30 are set forth in Table II.

TABLE II [Results of 52% formaldehyde stabilized with various amounts ofthe trimethyl silane-hydroxpropylmethyl cellulose] Percent concentrateDay 1 Day 3 Day 5 Day 12 Day 18 Day 28 0 l Clear Clear Clear Clear ClearCloudy do do do do 0 Do.

0.01 .do Hazy Cloudy, trace ppt Cloudy ppt Cloudy ppt Clear, l ra ppt.

0.005 do. Cloudy o Cloudy, M ppt... M ppt. cloudy o.

0.001 ..do Cloudy, trace ppt. ppt Clear, ppt Clear, ppt Clear, M" ppt.

goneclsmdy after 1 hr.) Clear, pp ppt., clear ppt., clear ppt., clearppt., clear 1" ppt., clear.

on re pared to organic halogenated silanes alone or in a mix- EXAMPLE IIturc. These results were surprising and indeed unobvious.

In a typical reaction of this invention, an organic halogenated silaneis added dropwise to methylcellulose in a solvent. After a short periodof time, the mixture is removed from the reaction vessel and the solventis allowed to evaporate. The remaining reaction product is then ready tobe used to stabilize formaldehyde solutions.

The organic halogenated silane may include trimethylchlorosilane,trimethylbromosilane, trichlorosilane, tetra- 55 chlorosilane,methyltrichlorosilane, phenyldimethylchlor A 2% aqueous solution ofhydroxypropylmethyl cellulose was prepared. More of the sameformaldehyde as was used in Example I was divided into 100 gm. samples.T0 different samples were added different amounts of the freshlyprepared hydroxypropylmethyl cellulose. The same concentrations wereused as were used in Example I and the results were compared. Thestabilized formaldehyde solutions of Example I were much less foamy whenshaken than those of Example II.

silane, trimethylfiuorosilane, triethylchlorosilane, diphenylmethylchlorosilane and so forth. However, for the pre- EXAMPLE HI ferredpractice of this invention trimethylchlorosilane is Ten grams of methylcellulose were mixed into 150 ml. used because of the outstandingresults obtained thereof anhydrous pyridine. Ten grams oftrimethylchlorosilane from. were then added dropwise with stirring intothe methylcel- For the long chain carbohydrate moiety cellulose etherslulose pyridine mixture. After stirring for about 5 minutes may be usedsuch as methylcellulose, ethylcellulose, prothe reaction was completedand the jelly-like solution pylcellulose, sodiumcarboxymet-hylcellulose, hydroxypoured out on a plate where the pyridinewas evaporated methyl celulose, hydroxyethylcellulose,hydroxypropylceloff. The resulting product was dissolved in enough waterlulose hydroxypropylmethylcellulose, hydroxyethylmethylto make a 1%solution. This solution was then ready for cellulose,ethylhydroxyethylcellulose, cyanoethylcellulose, use as a formaldehydestabilizer. benzylcellulose, sodium carboxymethyhydroxyethylcellu- Afreshly prepared aqueous solution of 52% formallose and the like. Again,because of superior results obdehyde was divided into 100 gm. samples.To different tained hydroxypropylmethyl cellulose is favored. sampleswere added different amounts of a freshly pre- In the preferred practiceof this invention hydroxypropared aqueous solution from avove. To thecontrol nothpylmethyl cellulose is mixed with anhydrous pyridine at ingwas added. All of the samples were then stored at a temperature of about20 C. To this mixture trimethyl- 45 C. The samples were periodicallychecked for cloudchlorosilane is added dropwise with constant stirring.After iness and precipitate formation. The results are set forth all thetrimethylchlorosilane is added stirring is continued in Table III.

TABLE III [Results of 52% formaldehyde stabilized with various amountsof the trimcthylchlorosilanemethylcellulose stabilizer] Percentconcentrate Dayl Day 4 Day 0.01 Clear Trace ppt., clondy M ppt., clear.

0.005 do ppt., cloudy m ppt., clear. None (control) ppt., cloudyclearppt ppt., clear.

EXAMPLE IV 10 What is claimed is:

A 1% aqueous solution of methylcellulose was prepared. More of the sameformaldehyde as was used in Example II was divided into 100 gm. samples.To the samples were added different amounts of the freshly preparedmethyl cellulose solution. The same concentrations were used as wereused in Example 11 and the results were compared. The stabilizedformaldehyde solutions of Example III were less foamy when shaken thanthose in Example IV and were less viscous and easier to handle.

EXAMPLE V Five grams (0.02 mol) of hydroxypropylmethyl cellulose and 2.2grams (0.02 mol) of trimethylchlorosilane are charged into a moisturefree reaction flask containing 60 mlrof dry toluene. The mixture issuspended with stirring and three drops of pyridine are added. Thereaction mixture is slowly heated to about 90 C. During the heat up timeHCl gas is detected in the off gas. At this point the reaction mixturehas turned dark brown. The heat is removed and the reaction is allowedto cool. The product is collected on a filter and washed with fresh drytoluene. The product is a very water soluble brown powder.

EXAMPLE VI Five grams (0.02 mol) of hydroxypropylmethyl cellulose and2.2 grams (0.02 mol) of trimethylchlorosilane are charged into amoisture free reaction flask containing 50 ml. of dry toluene. Themixture is suspended with stirring and 1-6 grams (0.02 mol) of pyridineis added and the temperature of the reaction mixture is noted to rise.The suspension becomes noticeably thicker and HCl gas is noted in theoff gas. After stirring for 30 minutes the white water soluble productis collected on a filter.

The invention has been described in detail for the purpose ofillustration but it will be obvious to those skilled in the art thatnumerous modifications and variations may be resorted to withoutdeparting from the spirit of the invention in its broadest aspects.

1. An aqueous solution of formaldehyde containing as a stabilizer thereaction product recovered from the reaction mixture obtained byreacting (A) an organic halo-- genated silane and (B) a long chaincarbohydrate, in the presence of pyridine, at a temperature ranging fromabout 20 C. to about C.

2. An aqueous solution of formaldehyde as defined in claim 1 wherein (A)is at least one member of the group consisting of trimethylchlorosilane,trimethylbromosilane, trichlorosilane, tetrachlorosilane,methyltrichlorosilane, phenyldimethylchlorosilane,diphenylmethylchlorosilane, trimethylfiuorosilane andtriethylchlorosilane and mixtures thereof.

3. An aqueous solution of formaldehyde as defined in claim 2 wherein (A)is trimethylchlorosilane.

4. An aqueous solution of formaldehyde as defined in claim 1 wherein (B)is at least one member of the group consisting of methylcellulose,ethylcellulose, propylcellulose, sodium carboxymethylcellulose,hydroxymethyl cellulose, hydroxyethylcellulose, hydroxypropylcellulose,hydroxypropylmethylcellulose, hydroxyethylmethylcellulose,ethylhydroxyethylcellulose, cyanoethyl cellulose, benzylcellulose andsodium carboxymethylhydroxyethylcellulose and mixtures thereof.

5. An aqueous solution of formaldehyde as defined in claim 4 wherein (B)is hydroxypropylmethylcellulose.

References Cited UNITED STATES PATENTS 3,532,756 10/1970 Prinz et al.260-606 FOREIGN PATENTS 20,613 12/1966 Japan 260-606 LEON ZITVER,Primary Examiner R. H. LILES, Assistant Examiner US. Cl. X.R. 260231

